Certain completions use screens and fill the annular space around the screens with particles known as proppant as an aid to controlling production of sand or other particulates from the formation and fracturing the formation. The proppant is prepared at the surface as a slurry and pumped downhole into a bottom hole assembly that extends through an isolation packer to the zone of interest. The bottom hole assembly has a series of screens. Inside the screens is a tool called a crossover that allows the slurry pumped down from the surface to get through the packer and then exit into an annular space below the packer and outside the screens. The gravel remains in the annular space outside the screens and the carrier fluid for the slurry enters a wash pipe inside the screen and goes into different porting in the crossover tool to get to the upper annulus above the set packer for the return trip back to the surface.
While proppant slurry is abrasive, its erosive effects are also directly related to its velocity which is also related to the pumped pressure. When delivery rates were lower, such as with gravel packing at lower flow rates and pressures, the erosion problem was present but manageable. More recently, the need for higher delivery rates and higher operating pressures such as when proppant delivery was also combined with formation fracturing has made the erosion problem more acute. The evolution to higher flow rates and operating pressures has also caused erosion to an outer tubular that extended around the crossover exit ports and which supported the screens below. The slurry had to impact this tubular before making an exit to the annular space around the screens. To protect this outer tubular from direct impingement from the high flow and high pressure slurry, abrasive resistant liners were placed inside made of a hardened material to extend the operating life of the assembly.
One response to the erosion problem, which is generally more severe at the location where the slurry is forced to change direction, has been to use inserts that are hardened and which are positioned literally in the ports where the slurry has to exit. This design is shown in U.S. Pat. No. 6,491,097 FIGS. 4A-4E. This approach was offered as an alternative to an earlier design that used a hardened ported sleeve inside the crossover with the sleeve ports aligned with ports in the crossover housing but having a smaller periphery so as to protect the edges of the crossover body ports from erosion by flowing slurry. This design is shown in U.S. Pat. No. 5,636,691. Other downhole valve designs have used inserts in ported sleeves that are shifted into and out of alignment with ports in a surrounding housing. One such design is shown in FIG. 4 of U.S. Pat. No. 6,973,974. Other designs of crossovers have attempted to reduce erosion after the exiting flow goes through the crossover ports and into an annulus defined by an outer tubular by reducing the energy of the flowing stream in that annular space by placing a hardened rotating member that is turned by the slurry stream as shown in U.S. Pat. No. 7,096,946. Protective sleeves at an inlet to a crossover have been used as shown in U.S. Pat. No. 5,597,040.
One of the issues with using an internal hardened sleeve is that it left the actual ports in the crossover housing unprotected in the portion of those ports that extended through the crossover wall. While an internal sleeve protected the crossover housing port interior edge at the inside housing wall, once the slurry got into the housing wall, the peripheral surface of the port through the wall and at the outer surface of the housing wall was left unprotected and suffered from erosion. That early design shown in U.S. Pat. No. 5,636,691 had these issues. The later design that put the inserts into the wall such as U.S. Pat. No. 6,491,097 protected the inside of the housing wall as the slurry passed through it but it had other disadvantages. The older internal sleeve design protected the inside surface of the crossover housing and going to just inserts in the ports through the wall of the crossover housing left the entire inside surface of the crossover housing exposed to erosive flow. Not only that but since the inserts were at most just flush with the internal housing wall at the housing ports and the interior housing wall was exposed, it left open an erosion path to start by removal of the interior housing wall around the periphery of the insert that was only in the wall. This opens a possibility of starting a bypass stream on the outside of the wall insert as the surrounding wall was eroded away. In severe cases the housing port could be enlarged enough to undermine the support for the insert.
The present invention seeks to overcome these shortcomings of the prior design by allowing an insert assembly to be employed that protects the passage through the housing wall where the slurry exits through ports and also affords interior wall protection to the housing inside wall and inside edges of the wall ports in the housing. A series of erosion resistant inserts are inserted into wall openings. The inserts include a segment that extends through the wall opening and an interior flange that straddles the wall opening on the inside surface and in the preferred embodiment covers the inside wall from erosive effects. The inserts can be configured to keep each other in position or they can be secured to the housing or to each other. Edges of the inserts can be made to overlap inside the crossover housing to hold them in place or to better secure the interior housing wall from erosion from slurry that might otherwise work a path to the inside housing wall between abutting inserts. These and other features of the present invention will become more clear to those skilled in the art from a review of the discussion of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is determined from the associated claims.